Much recent evidence has pointed to a primary role of matrix vesicles in biological calcification. The objectives of the proposed research are to elucidate the role of matrix vesicles in the initiation and regulation of biological calcification. Primary emphasis will be placed on 1) biochemical characterization of the matrix vesicles (re. mineral, protein, enzyme, lipid and other organic constituents), and 2) studying their metabolism relative to mineral formation (Ca45 and P32 uptake and deposition), vesicle formation and destruction (re. lipid biosynthesis and degradation). Special emphasis will be placed on the role of alkaline phosphatase and possible lipid-calcium phosphate-complexes in de novo mineral formation by matrix vesicles, areas which past work indicates should be particularly valuable. Because of the abundance of tissue provided and the relative ease of experimental manipulation, the epiphyseal plate of broiler chickens will be utilized as the source of tissue from which will be isolated chondrocytes (and subcellular organelles) and matrix vesicles - by both enzymatic and non-enzymatic methods. The constituents of the matrix vesicles will be characterized by chemical, chromatographic (column, thin-layer, gas-liquid, high-pressure liquid, and two-dimensional silica gel-loaded paper), electrophoretic (SDS-PAGE and conventional PAGE), enzymatic, spectroscopic (UV, IR, laser-Raman, and NMR), atomic absorption, x-ray diffraction and electron microscopic procedures.